1. Field of the Invention
The present invention is generally related to devices for drawing blood samples from a human patient, and is more particularly related to such devices as employ a double-ended blood collection needle in which one end of the needle is inserted hypodermically into the blood vessel, and the other end of the needle pierces the stopper of an evacuated blood-collection tube, whereby the blood is drawn through the needle into the blood-collection tube.
2. Description of the Related Art
A popular method and apparatus currently in use for drawing blood samples includes essentially three separate components. The first component is an evacuated blood-collection tube, generally shaped like a chemist's test tube and having the open end sealed with a stopper of rubber or a rubber-like material. The blood collection tube is supplied pre-evacuated and with at least the interior surfaces of the tube and stopper sterilized. The tube is usually made of glass, and can be cleaned, autoclaved, evacuated and stoppered anew by the supplier, if desired, although the tube can also be disposed of after one use, as economics and good health care practice may dictate. The second component is a hollow blood-collection needle which is essentially a stainless steel cannula sharpened at both ends, with a hub of some sort bonded about the needle intermediate the two ends. As supplied, the hub is usually located off center with respect to the length of the needle, at a point closer to the end which is ultimately used to pierce the rubber stopper. Incidentally, the end used to pierce the rubber stopper, while having a beveled point, usually has the very tip of the beveled point bent over slightly toward the longitudinal axis of the needle. This construction allows the end of the needle to puncture the rubber stopper without cutting a rubber core plug which would obstruct the needle The hub of the blood collection needle can have flanges which extend radially outwardly perpendicular to the needle, or screw threads on its outer surface, depending upon the particular manufacturer's chosen design. In either case, the flanges or screw threads have the purpose of engaging and being tightly held by appropriately mating surfaces of a needle holder, which is the third component, described further below. The needle and hub assembly, like the blood-collection tube, is supplied sterile, and furthermore the ends of the needles are physically guarded and kept sterile by a two-part sheath made of relatively rigid plastic. Each half of the sheath is placed over its respective end of the needle, the two halves meeting at the hub where a breakable seal is effected between the halves. The sheath half overlying the working (blood vessel puncturing) end of the needle also has a ribbed and grooved internal configuration which cooperatively mates with a similar ribbed and grooved outer surface of the hub, so that the sheath half can be used as a tool to rotate the needle/hub assembly to engage it with the needle holder. The third element is a needle holder which is essentially a plastic tube of slightly larger diameter than the blood collection tube, closed at one end except for a hole through which the stopper piercing portion of the blood collection needle can pass into the interior of the needle holder. The exterior of the closed end of the needle holder includes appropriately shaped surfaces for engaging the flanges or exterior threads of the needle hub, thereby holding the needle hub fast to the end of the needle holder when the needle hub is inserted therein and turned appropriately. Such engagement is accomplished in the one case by causing the radially extending hub flanges to be rotated so that they are wedged below overlying portions of the plastic holder, and in the other case by causing the hub external threads to be screwed into the corresponding internal threads of the plastic holder. Drawings and additional descriptions of the prior art apparatus are shown in U.S. Pat. No. 3,890.955, issued June 24, 1975 to Elliot.
The above described three-element apparatus is used in the following way. The seal between the two halves of the blood collection needle sheath is broken, and the half covering the stopper-piercing end of the needle is removed. Holding the blood collecting needle by the remaining sheath portion, the exposed end of the needle is inserted through the aperture in the end of the needle holder, and the sheath is turned to engage the needle hub with the needle holder. The stoppered end of the blood collection tube is inserted into the open end of the needle holder, but the stopper is not allowed to be pierced yet. The sheath covering the working end of the needle is removed, and the exposed needle, now securely attached to the needle holder, is inserted hypodermically into the blood vessel of the patient. While holding the needle stationary with respect to the patient, the blood collection tube is pushed up into the needle holder until the stopper is pierced by the end of the needle extending into the needle holder, whereby the needle is in communication with the evacuated interior of the blood collection tube, and blood is drawn through the needle into the tube.
If additional blood need be drawn, the blood collection tube can be withdrawn from the needle holder, leaving the needle in place in the blood vessel, and a fresh blood collection tube can be inserted into the needle holder and additional blood collected. When the required amount of blood has been withdrawn, the last blood collection tube is withdrawn from the needle holder, and the needle holder and needle are withdrawn from the patient in unison.
Since the needle and hub assemblies are disposable, but the needle holders are reusable, the needle must be disengaged from the needle holder so that the needle can be disposed of, and the needle holder preserved. In order to do this, the working end of the needle (which has just been withdrawn from the patient) must be resheathed so that the sheath can be used as a tool to disengage the needle hub from the needle holder, just as it was used in the first instance as a tool to engage the two.
Herein lies a grave danger to the medical technician. The act of resheathing a used needle is quite dangerous, as it is easy to miss and stick one's finger on the bloody needle. The technician risks contracting any blood borne disease the patient may have, such as hepatitis or AID$. For this reason, public health authorities recommend that used needles not be resheathed. Nevertheless, for the sake of economics, resheathing is routinely practiced as the most expedient way to disengage the needle from the needle holder so that the needle holder, which has not been contaminated, can be reused.
The present invention avoids resheathing by a novel design of the needle holder wherein the means for engaging and disengaging the needle hub with respect to the needle holder is part of the needle holder itself, thereby making it unnecessary for the technician's hand to come anywhere near the sharp end of the used needle.